Welcome to the forum!
Is that image with a deer, a raster image? Or is it something you've already drawn with Inkscape, and it's vector paths? As I was reading your message, I got the idea you had already drawn the deer (or maybe something else) in Inkscape, and you wanted to add more details.
If that's the case, then it depends on what kind of " little lines of detail " you want to add. Personally, I have no idea what you've seen in other designs. It could be that you can draw them with the Pen or Pencil tool. But depending on the details, Inkscape might have a tool that would create what you want.
If they are fairly simple details, you might not even need to draw them. You might be able to use the Node tool, and do some node editing to create the details.
So if you're talking about editing a vector file, please give us some more details about the details (yuk-yuk) which you want to create. Or maybe even some images showing what you want to achieve. Then we can give you some ideas how to do it.